Borane Adducts of Aromatic Phosphorus Heterocycles: Synthesis, Crystallographic Characterization and Reactivity of a Phosphinine-B(C6 F5 )3 Lewis Pair.

A phosphinine-borane adduct of a Me3 Si-functionalized phosphinine and the Lewis acid B(C6 F5 )3 has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B2 H6 with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine-borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct (6-B(C6 F5 )3 ) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me3 Si-C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts.

Phospholenes from Phosphabenzenes by Selective Ring Contraction.

A 3-amino-functionalized phosphabenzene (phosphinine) has been synthesized and structurally characterized. The pyramidalized nitrogen atom of the dimethylamino substituent indicates only a weak interaction between the lone pair of the nitrogen atom and the aromatic phosphorus heterocycle, resulting in somewhat basic character. It turned out that the amino group can indeed be protonated by HCl. In contrast to pyridines, however, the phosphabenzene-ammonium salt undergoes a selective ring contraction to form a hydroxylphospholene oxide in the presence of additional water. Based on deuterium labeling experiments and quantum chemical calculations, a rational mechanism for this hitherto unknown conversion is proposed.

Photochemically deoxygenating gels for triplet-triplet annihilation photon-upconversion performed under air.

For an efficient triplet-triplet annihilation photon upconversion (TTA-UC) process, matrices in which sensitizers and emitters are dispersed should not only allow molecular diffusions but also protect triplet excited states from oxygen-quenching. In this work, two photochemically deoxygenating gels, a poly(N-vinyl-2-pyrrolidone) (PVP) gel and a limonene gel, were prepared for TTA-UC performed under air. These two gels are optically transparent in the visible region and can serve as a scavenger for sensitized singlet oxygen. For the green-to-blue couple of platinum(II) octaethylporphyrin (Pt(OEP)) and 9,10-diphenylanthracene (DPA), under air, the bimolecular quenching rate constants were 6.73 × 108 dm3 mol-1 s-1 for the PVP gel and 1.54 × 109 dm3 mol-1 s-1 for the limonene gel, and the upconversion quantum yields were 9.1% and 1.9% in PVP and limonene gels, respectively. As matrices, the PVP gel can be employed in NIR-to-yellow, red-to-cyan, green-to-blue and blue-to-violet TTA-UC systems operating under air. TTA-UC systems of Pt(OEP)/DPA in PVP or limonene gels showed strong upconverted emission under air with non-coherent light of low optical power density as the excitation source.

Making Aromatic Phosphorus Heterocycles More Basic and Nucleophilic: Synthesis, Characterization and Reactivity of the First Phosphinine Selenide.

The synthesis and isolation of a phosphinine selenide was achieved for the first time by reacting red selenium with 2,6-bis(trimethylsilyl)phosphinine. The rather large coupling constant of 1 JP,Se =883 Hz is in line with a P-Se bond of high s-character. The σ-electron donating Me3 Si-substituents significantly increase the energy of the phosphorus lone pair and hence its basicity, making the heterocycle considerably more basic and nucleophilic than the unsubstituted phosphinine C5 H5 P, as confirmed by the calculated gas phase basicities. NBO calculations further reveal that the lone pairs of the selenium atom are stabilized through donor-acceptor interactions with antibonding orbitals of the aromatic ring. The novel phosphinine selenide shows a distinct reactivity towards hexafluoro-2-butyne, Au(I)Cl as well as i PrOH. Our results pave the way for new perspectives in the chemistry of phosphorus in low coordination.

A Prototype of a Volumetric Three-Dimensional Display Based on Programmable Photo-Activated Phosphorescence.

A proof-of-principle prototype of a volumetric 3D-displaying system is demonstrated by utilizing the photo-activated phosphorescence of two long-lived phosphorescent metal-porphyrins in dimethyl sulfoxide (DMSO), a photochemically deoxygenating solvent. The first phosphorescent sensitizer, Pt(TPBP), absorbs a light beam with a wavelength of 635 nm, and the sensitized singlet oxygen is scavenged by DMSO. The second phosphorescent emitter, Pt(OEP), absorbs a light beam with a wavelength of 532 nm and visibly phosphoresces only in the deoxygenated zone generated by the first sensitizer. The phosphorescent voxels, 3D images, and animations are well-defined by the intersections of the 635-nm and 532-nm light beams that are programmable by tuning of the excitation-power densities, the beam shapes, and the kinetics. As a pivotal selection rule for the phosphorescent molecular couple used in this 3D-displaying system, their absorptions and emissions must be orthogonal to each other, so that they can be excited and addressed independently.

Combined inhibition of EGFR and c-ABL suppresses the growth of fulvestrant-resistant breast cancer cells through miR-375-autophagy axis.

Fulvestrant is the FDA-approved "pure anti-estrogen" agent for malignant breast cancer therapy. But endocrine resistance causes drug failure. A new approach is desired for fulvestrant-resistant breast cancer (FRBC) therapy. This study aims to find an effective approach to inhibit FRBC for patients with advanced breast cancer. MTT assay was first performed to detect the effect of inhibitors of c-ABL (imatinib) and EGFR (lapatinib) on FRBC cells. Microarray analysis was carried out to identify microRNA which is significantly changed between parental and FRBC cells. The related mechanisms were analyzed by qRT-PCR, MTT, AO staining and western blotting. Dual treatment significantly inhibited cell growth of FRBC and upregulated microRNA-375 (miR-375). Overexpression of miR-375 inhibited growth of FRBC cells, reduced autophagy, and decreased expression of ATG7 and LC3-II. Dual treatment elevated expression of miR-375 more than any single one of these two inhibitors. Overexpression of miR-375 increased cell growth inhibition induced by dual treatment, and the effect was attenuated when miR-375 was inhibited. In conclusion, we identified that combined inhibition of EGFR and c-ABL can suppress the growth of FRBC cells and elucidated a mechanism within FRBC cells involving regulation of miR-375 and autophagy. Dual treatment may be useful for inhibiting fulvestrant-resistant breast cancer.

Phosphinine Selenide: Noncovalent Interactions with Organoiodines and Elemental Iodine, and Reactivity towards Potassium Cyanide.

A co-crystalline adduct consisting of a phosphinine selenide and an organohalide was obtained by slow evaporation of the solvent from a mixture of 2,6-bis(trimethylsilyl)phosphinine selenide and 1,4-diiodotetrafluorobenzene (1,4-TFDIB). The crystallographic characterization of the product shows π-π stacking, F⋅⋅⋅H hydrogen bonding between 1,4-TFDIB and the phosphinine selenide, as well as F⋅⋅⋅F interactions between 1,4-TFDIB molecules. Moreover, the phosphorus heterocycle could be crystallized with diiodine to form a 1 : 1 adduct. The d(I-I) distance in this compound is 2.8475(3) Å, which is shorter than the corresponding one in triphenylphosphine selenide diiodide, reflecting the weaker net-donor power of the phosphinine selenide towards diiodine. The phosphinine selenide could also be used as a selenium transfer reagent to generate KSeCN from KCN.

Phosphinine Selenide: Noncovalent Interactions with Organoiodines and Elemental Iodine, and Reactivity towards Potassium Cyanide.

Invited for this month's cover is the group of Prof. Dr. Christian Müller from Freie Universität Berlin, Germany. The cover picture shows a phosphinine selenide that interacts with organoiodines and halogens to form co-crystalline and charge-transfer adducts. More information can be found in the Research Article by Christian Müller and co-workers.

Photo-writing self-erasable phosphorescent images using poly(N-vinyl-2-pyrrolidone) as a photochemically deoxygenating matrix.

A passive photo-writing approach for optical data recording is described. Poly(N-vinyl-2-pyrrolidone) has been demonstrated as a photochemically deoxygenating polymeric matrix in which phosphorescent images from a molecular phosphor could be written by photo-activation and be competitively erased by diffusional oxygen quenching.

Photochemically deoxygenating solvents for triplet-triplet annihilation photon upconversion operating in air.

Sulfoxides and cyclic ureas are photochemically deoxygenating solvents in which the oxidative stress could be released and efficient triplet-triplet annihilation photon upconversion (TTA-UC) can operate in air. Such solvents can be practically screened out by harnessing the property of photo-activated phosphorescence.